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A gaseous hydrocarban (A) is converted i...

A gaseous hydrocarban (A) is converted into another (B) by consuming 2 mol `H_2` in the presence of Ni catalyst. B can be prepared by the reaction between methyl iodide and metallic sodium in dry ether medium. Identify the two hydrocarbon (A and B ) and mention the reactions involved.

Text Solution

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In hydrogenation `(H_(2)//Ni)` reaction, one mole of the hydrocarbon (A) accepts two moles of hydrogen. So, the hydrocarbon (A) is an unsaturated hydrocarbon which either contains two double bonds or one triple bond. In ether medium, the reaction between methyl iodide and metallic sodium yields the hydrocarbon (B). This is Wurtz reaction and in this reaction, ethane `(CH_(3)CH_(3))` is formed,
`CH_(3) -I + 2Na + I - CH_(3) underset("Wurtz reaction")overset("Dry ether")rarr underset("Ethane")(CH_(3) - CH_(3)) + 2NaI`
Therefore, the hydrocarbon (B) is ethane. Since the hydrocarbon (A) gives ethane by absorbing 2 moles of `H_(2)`, it must contain a triple bond (two double bonds cannot be formed between two carbon atoms) and obviously it is acetylene `(H - C -= C-H)`
`H-C-=C - H+ 2H_(2) overset(Ni)rarr CH_(3) - CH_(3)` (Ethane)
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